The Myth That Measles Never Left

That translates into about 500,000 reported cases each year. Technically, it was likely closer to about 4 million cases in the United States each year, but either way, we know that lots of people got measles.

Then we got a measles vaccine and not surprisingly, cases of measles dropped. Except for a small uptick from 1989 to 1991, we were on our way to eliminating measles.

And we did, in 2000, when the endemic spread of measles was eliminated in the United States. From then on, all measles cases were imported.

In 2004, we had an historic low of just 37 measles cases in the United States!

Will we ever have fewer than 37 cases in a year?

And from 2000 to 2012, we averaged just 87 measles cases each year, which is far below the US average of 283 cases we are now seeing.

And in areas of the world where measles is still highly endemic, you can expect cycles of larger measles epidemics every 1 to 4 years.

Can you guess why?

“As higher uniform population immunity is achieved the scale of epidemics, both their duration and absolute number of cases, progressively decreases. Epidemic frequency simultaneously decreases with increasing time intervals between epidemics. Another uniform feature as elimination is approached is the loss of epidemic seasonality.”

Durrheim et al on Measles – The epidemiology of elimination

I’ll give you a hint – there is nothing different about the measles virus during those years.

Eventually though, as the number of people susceptible to measles builds up, there is the opportunity for bigger outbreaks. Of course, that doesn’t happen if most people are vaccinated and protected.